Composition and method for remediation of near wellbore damage

ABSTRACT

Aspects of the invention relate to compositions and methods that are used for remediation of near-wellbore damage. A specific aspect is a composition comprising an olefin sulfonate, a sulfosuccinate, and a chemical selected from the group consisting of an alcohol alkoxylated sulfate, an alcohol alkoxylated carboxylate, or a combination thereof.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/800,386, filed on Mar. 15, 2013, which is incorporated in full byreference.

TECHNICAL FIELD

The present disclosure generally relates to a composition and method forremediation of near wellbore damage. In particular cases, the presentdisclosure concerns a composition comprising a C₂₀₋₂₈ internal olefinsulfonate and a chemical selected from the group consisting of a C₁₅₋₁₈internal olefin sulfonates, an alcohol alkoxylated sulfate, an alcoholalkoxylated carboxylate, a sulfosuccinate and a combination thereof. Thepresent disclosure also relates to a method of injecting the compositioninto a well to remediate near wellbore damage.

BACKGROUND

Reservoir systems, such as petroleum reservoirs, typically containfluids such as water and a mixture of hydrocarbons such as oil and gas.To remove (“produce”) the hydrocarbons from the reservoir, differentmechanisms can be utilized such as primary, secondary or tertiaryrecovery processes.

In a primary recovery process, hydrocarbons are displaced from areservoir through the high natural differential pressure between thereservoir and the bottomhole pressure within a wellbore. The reservoir'senergy and natural forces drive the hydrocarbons contained in thereservoir into the production well and up to the surface. Artificiallift systems, such as sucker rod pumps, electrical submersible pumps orgas-lift systems, are often implemented in the primary production stageto reduce the bottomhole pressure within the well. Such systems increasethe differential pressure between the reservoir and the wellbore intake;thus, increasing hydrocarbon production. However, even with use of suchartificial lift systems only a small fraction of theoriginal-oil-in-place (OOIP) is typically recovered using primaryrecovery processes as the reservoir pressure, and the differentialpressure between the reservoir and the wellbore intake declines overtimedue to production. For example, typically only about 10-20% of the OOIPcan be produced before primary recovery reaches its limit, either whenthe reservoir pressure is so low that the production rates are noteconomical or when the proportions of gas or water in the productionstream are too high.

In order to increase the production life of the reservoir, secondary ortertiary recovery processes can be used. Secondary recovery processesinclude water or gas well injection, while tertiary methods are based oninjecting additional chemical compounds into the well, such assurfactants and polymers. Typically in these processes, fluids areinjected into the reservoir to maintain reservoir pressure and drive thehydrocarbons to producing wells. An additional 10-50% of OOIP can beproduced in addition to the oil produced during primary recovery.

While secondary and tertiary methods of oil recovery can further enhanceoil production from a reservoir, care must be taken in choosing theright processes and chemicals for each reservoir, as some methods maycause formation damage or plugging. Damage can occur in the formationeven with the careful choice of chemicals during enhanced oil recoveryprocesses. The near wellbore area is especially prone to damage as it issubjected to higher concentrations of enhanced oil recovery chemicals.Additionally, water and steam flooding can cause fines migration whichmay eventually plug pores, while surfactant flooding can cause a buildupof polymers within the pores of the reservoir. Other near wellboredamage can include changes in wettability due to oil wet solids, such asthrough the build up in the formation of asphaltenes and paraffin.

SUMMARY

A general embodiment of the disclosure is a composition comprisingC₂₀₋₂₈ internal olefin sulfonate and two or more chemicals selected fromthe group consisting of C₁₅₋₁₈ internal olefin sulfonates, an alcoholalkoxylated sulfate, an alcohol alkoxylated carboxylate, and asulfosuccinate. In certain embodiments, the composition comprises aC₂₀₋₂₈ internal olefin sulfonate, a sulfosuccinate, and an alcoholalkoxylated sulfate. In specific embodiments, the composition comprisesC₂₀₋₂₈ internal olefin sulfonate, C₁₅₋₁₈ internal olefin sulfonates, andan alcohol alkoxylated carboxylate. The sulfosuccinate may be sodiumdihexyl sulfosuccinate or dianyl sulfosuccinate, and the dihexylsulfosuccinate can be partially derived from a 4-methyl-2-pentanolfeedstock. In embodiments, the alcohol alkoxylated sulfate isTDA-8(PO)-SO₄ ⁻, TDA-4(PO)-SO₄ ⁻, TDA-12(PO)-SO₄ ⁻, or the salt thereof.In certain embodiments, the C₂₀₋₂₈ internal olefin sulfonate is anisomerized C₂₀₋₂₈ alpha olefin sulfonate, such as a isomerized C₂₀₋₂₈alpha olefin sulfonate comprises about 20-98 percent branching. Thecomposition can further comprise a co-solvent, such as EGBE, isopropylalcohol, ethanol, n-propyl alcohol, n-butyl alcohol, sec-butyl alcohol,n-amyl alcohol, sec-amyl alcohol, n-hexyl alcohol, sec-hexyl alcohol,polyalkylene alcohol ethers, polyalkylene glycols,poly(oxyalkylene)glycols, or (oxyalkylene)glycols ethers. Each chemicalcan comprise between 0.5% by weight to 15% by weight of the compositionor 0.5% and 3% by weight of the composition. The composition canadditionally comprise seawater or produced reservoir brine water.

Another general embodiment is a method for near-wellbore damageremediation comprising injecting into a subterranean reservoir acomposition comprising a C₂₀₋₂₈ internal olefin sulfonate and two ormore chemicals selected from the group consisting of a C₁₅₋₁₈ internalolefin sulfonate, an alcohol alkoxylated sulfate, an alcohol alkoxylatedcarboxylate, and a sulfosuccinate. The injection of the composition canstimulates the reservoir, such as by improving the relative permeabilityof the reservoir. The improvement in relative permeability may be by250% or more. After injection of the composition, the well may beshut-in. In embodiments, injection of the composition remediates damagein the near-wellbore region of the reservoir. In specific embodiments,the temperature of the reservoir is above 55° C. In this case thecomposition can comprise a C₂₀₋₂₈ internal olefin sulfonates, an alkali,a C₁₅₋₁₈ internal olefin sulfonates, and an alcohol alkoxylatedcarboxylate. In other embodiments, the temperature of the reservoir isbelow 55° C. In this case, the composition can comprise a C₂₀₋₂₈internal olefin sulfonate, an alcohol alkoxylated sulfate, and asulfosuccinate. The alcohol alkoxylated sulfate can be TDA-8(PO)-SO₄ ⁻,TDA-4(PO)-SO₄ ⁻, TDA-12(PO)-SO₄ ⁻ or the salt thereof. Thesulfosuccinate can be sodium dihexyl sulfosuccinate or dianylsulfosuccinate. The composition can further comprise a co-solvent, suchas EGBE, isopropyl alcohol, ethanol, n-propyl alcohol, n-butyl alcohol,sec-butyl alcohol, n-amyl alcohol, sec-amyl alcohol, n-hexyl alcohol,sec-hexyl alcohol, polyalkylene alcohol ethers, polyalkylene glycols,poly(oxyalkylene)glycols, or (oxyalkylene)glycols ethers. Further, thereservoir into which the composition is injected can comprise polymeremulsion damage, such as from a previous chemically enhanced oilrecovery flood. The method can further comprise initiating production ofthe reservoir after injecting the composition.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter. It should be appreciated by those skilled in the art thatthe conception and specific embodiments disclosed may be readilyutilized as a basis for modifying or designing other structures forcarrying out the same purposes of the present invention. It should alsobe realized by those skilled in the art that such equivalentconstructions do not depart from the scope of the invention as set forthin the appended claims. The novel features which are believed to becharacteristic of the invention, both as to its organization and methodof operation, together with further objects and advantages will bebetter understood from the following description when considered inconnection with the accompanying figures. It is to be expresslyunderstood, however, that each of the figures is provided for thepurpose of illustration and description only and is not intended as adefinition of the limits of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawings.

FIG. 1 is an illustration of a damage remediation composition entering asubterranean reservoir.

FIG. 2 is a graph showing relative permeability per pore volume injectedof a core flood. The first arrow indicates the injection of aremediation composition without C₂₀-C₂₈ IOS, while the second arrowindicates the injection of a remediation composition with C₂₀-C₂₈ IOS.

FIG. 3 is a graph showing relative permeability per pore volume injectedof a core flood. The diamonds represent the injection of a polymersolution, while the squares represent the injection of a remediationcomposition of the disclosure.

FIG. 4 is a graph showing relative permeability per pore volume injectedof a core flood. The squares at 0-5 PVs represent the injection of aremediation composition of the disclosure, while the diamonds at 5-20 PVrepresent the injection of a polymer solution, and the diamonds from20-24 PV represent the injection of a remediation composition of thedisclosures.

FIG. 5 is a graph showing relative permeability per pore volume injectedof a core flood. The squares represent the injection of a polymersolution, while the diamonds represent the injection of a remediationcomposition of the disclosure.

FIG. 6 is a graph showing the change in the relative permeability perpore volume injected of a core flood.

FIG. 7a-i are snapshots taken after injecting a remediation compositionof the present disclosure into a fish tank core flood.

DETAILED DESCRIPTION

In the enhanced oil recovery process, the addition of surfactants andpolymers improves oil recovery significantly. However, the use of thesematerials over time can build up, causing damage and plugging in theformation near the wellbore. Aspects of the present invention describe acomposition and a method for near wellbore damage remediation.Specifically, an embodiment of the invention is a composition comprisinga C₂₀₋₂₈ internal olefin sulfonate and a chemical selected from thegroup consisting of a C₁₅₋₁₈ internal olefin sulfonates, an alcoholalkoxylated sulfate, an alcohol alkoxylated carboxylate, asulfosuccinate and a combination thereof. The present disclosure alsorelates to a method of injecting the composition into a well toremediate near wellbore damage.

As used herein, the term “equal” refers to equal values or values withinthe standard of error of measuring such values. The term “substantiallyequal” or “about” refers to an amount that is within 3% of the valuerecited.

As used herein, “a” or “an” means “at least one” or “one or more” unlessotherwise indicated.

“Effective amount,” as used herein, refers to an amount of a componentsufficient increase the relative permeability of a wellbore.

“Pore volume” or “PV” fraction as used herein refers to the total volumeof pore space in the oil reservoir that is contemplated in a sweep.

“Relative permeability” refers to the ratio of the effectivepermeability for a particular fluid to a reference or base permeabilityof the rock. Here, the relative permeability of water in cores iscalculated using Darcy's law as follows:k _(rw) =q*μ*L/(k*A*ΔP)

where k_(rw) is the relative permeability of water, q is the flow rate,μ is the viscosity, L is the length, k is the brine permeability, A isthe cross-sectional area, and ΔP is the pressure drop. “Near wellbore”refers to the region of the reservoir which is located near to thewellbore in which the damage remediation composition was injected. Forexample, the near wellbore region could be within a few inches, such asbetween 2 and 12 inches of the wellbore, within a few feet, such as 1-10ft, of the wellbore, or within tens of feet, such as 20-50, of thewellbore.

FIG. 1 illustrates an example subterranean reservoir which includes aninjection well 11 which extends to a portion of a subsurface reservoir13 containing hydrocarbons for production, such that injection well 11is in fluid communication with subsurface reservoir 13 and thehydrocarbons. Production well 15 is also in fluid communication withreservoir 13 in order to receive the hydrocarbons. Production well 15 ispositioned a lateral distance away from injection well 11. While wellinjection and projection wells are shown in FIG. 1, it should beunderstood that the method may also be practiced in any type of well.The remediation composition may also be used in a shut-in typeprocedure. As shown in FIG. 1, the remediation composition 17 isinjected through the injection well 11 into reservoir 13.

Remediation Composition

Embodiments of the disclosure are directed to a composition for theremediation of near wellbore damage. The remediation compositioncomprises a C₂₀₋₂₈ internal olefin sulfonate and a chemical selectedfrom the group consisting of a C₁₅₋₁₈ internal olefin sulfonates, analcohol alkoxylated sulfate, an alcohol alkoxylated carboxylate, asulfosuccinate and a combination thereof. The remediation compositionmay be premixed to create a concentrated mixture of the differentcomponents. In this case, the remediation composition comprises over 20%each of a C₂₀₋₂₈ internal olefin sulfonate and a chemical selected fromthe group consisting of a C₁₅₋₁₈ internal olefin sulfonates, an alcoholalkoxylated sulfate, an alcohol alkoxylated carboxylate, asulfosuccinate and a combination thereof. The concentrated compositionmay be diluted to a lower concentration prior to injecting theremediation composition into a subterranean reservoir. For example, asoftened brine water may be used to dilute the components of thecomposition down to less than 30%, less than 20%, or less than 15% eachof the diluted composition. The composition may comprise each chemicalcomponent in equal quantities, or the quantities of each component maybe different. The remediation compositions may be optimized for acertain reservoir and/or a certain type of damage. For example, aremediation composition for use in a high temperature reservoir maycomprise C₂₀₋₂₈ internal olefin sulfonates and an alcohol alkoxylatedcarboxylate at a ratio of 1:2. While, in another example, a remediationcomposition for use in a low temperature reservoir may comprise C₂₀₋₂₈internal olefin sulfonates, an alcohol alkoxylated sulfate, and asulfosuccinate at a ratio of 1:1:1.

Not to be limited by theory, the remediation composition comprises oneor more surfactants which dissolve and clean emulsion damage, and asurfactant which solubilizes the emulsion to help flush it away from thewellbore. In a specific embodiment of the invention, the remediationcomposition comprises three different surfactants, or four or moredifferent surfactants. In an embodiment, the wellbore damage resides ina low temperature reservoir (less than 55° C.) and theemulsion-dissolving surfactants comprise a sulfosuccinate and an alcoholalkoxylated sulfate, while the solubilizing surfactant comprises C₂₀₋₂₈IOS. In another embodiment, the wellbore damage resides in a hightemperature reservoir (greater than 55° C.) and the remediationcomposition comprises an alkali, a C₁₅₋₁₈ IOS, an alcohol alkoxylatedcarboxylate, and a C₂₀₋₂₈ IOS. This method of both cleaning andsolubilizing emulsion damage in a reservoir not only stimulates the wellafter the cleanout, but damage to the well after the cleanout with theremediation composition occurs at a slower rate (see Example 5 and FIG.6).

The amounts of surfactants in the remediation composition can vary. Forexample, each surfactant in the composition can between 0.1-25%,0.5-15%, or 1%-5% by weight of the composition. The concentration of thecomposition usually depends on the volume that is to be injected intothe wellbore. For example, if a small volume is injected, thecomposition may have a higher concentration of surfactants. If a largevolume is injected, the composition may have a lower concentration ofsurfactants. The surfactants are usually comprised in an aqueoussolution, such as brine water or softened seawater.

Internal Olefin Sulfonate

As used herein, “internal olefin sulfonates” or “IOS” refers to anunsaturated hydrocarbon compound comprising at least one carbon-carbondouble bond and at least one SO₄ ⁻ group, or a salt thereof. As usedherein, a “C₂₀-C₂₈ internal olefin sulfonate” or “C₂₀-C₂₈ IOS” refers toan IOS, or a mixture of IOSs with an average carbon number of 20 to 28,or of 23 to 25. The C₂₀-C₂₈ IOS may comprise at least 80% of IOS withcarbon numbers of 20 to 28, at least 90% of IOS with carbon numbers of20 to 28, or at least 99% of IOS with carbon numbers of 20 to 28. Asused herein, a “C₁₅-C₁₈ internal olefin sulfonate” or “C₁₅-C₁₈ IOS”refers to an IOS or a mixture of IOSs with an average carbon number of15 to 18, or of 16 to 17. The C₁₅-C₁₈ IOS may comprise at least 80% ofIOS with carbon numbers of 15 to 18, at least 90% of IOS with carbonnumbers of 15 to 18, or at least 99% of IOS with carbon numbers of 15 to18. The internal olefin sulfonates may be alpha olefin sulfonates, suchas an isomerized alpha olefin sulfonate. The internal olefin sulfonatesmay also comprise branching. In certain embodiments, C₁₅-C₁₈ IOS may beadded to the wellbore remediation composition when used in hightemperature reservoirs, such as reservoirs above 55° C. The IOS may beat least 20% branching, 30% branching, 40% branching, 50% branching, 60%branching, and 65% branching. In some embodiments, the branching isbetween 20-98%, 30-90%, 40-80%, or around 65%. Examples of internalolefin sulfonates and the methods to make them are found in U.S. Pat.No. 5,488,148, U.S. Patent Application Publication 2009/0112014, and SPE129766, all incorporated herein by reference.

In embodiment of the disclosure, the IOS comprises 0.1-15% by weight ofthe wellbore remediation composition to be injected into a reservoir. Incertain embodiments of the disclosure the IOS comprises 0.5% to 5% byweight of the wellbore remediation composition. In a specificembodiment, the IOS comprises about 1% by weight of the wellboreremediation composition.

As disclosed here, C₂₀-C₂₈ IOS solubilizes crude oil and the addition ofa C₂₀-C₂₈ IOS acts synergistically with emulsion-dissolving surfactantsto remove damage to a formation and to stimulate a reservoir. Example 1and FIG. 5 illustrate the synergistic response of including C₂₀-C₂₈ IOSin a remediation composition with emulsion-dissolving surfactants. Thecomposition of the C₁₅-C₁₈ IOS is generally tailored to the conditionsof the reservoir needing damage remediation.

Alcohol Alkoxylated Sulfate

Embodiments of the disclosure include the addition of an alcoholalkoxylated sulfate in the remediation composition. The alcoholalkoxylated sulfate has the general structure of alcohol-PO/EO-SO₄ ⁻, ora salt thereof. The alcohol group comprises 10-32 carbon atoms, and inspecific embodiments comprises between 16 to 32, 13 to 17, or 10 to 13carbon atoms. In embodiments of the invention the PO/EO group comprises0-50 ethylene oxide groups, 0-50 propylene oxide groups, or combinationsthereof. The alcohol alkoxylated sulfate may be the salt of the alcoholalkoxylated sulfate, such as a sodium alcohol alkoxylated sulfate. Inspecific embodiments of the invention the alcohol alkoxylated sulfate isa tridecyl-8(propylene oxide)-sulfate (TDA-8(PO)-SO₄ ⁻). In otherembodiments of the invention the alcohol alkoyxlated sulfate isTDA-4(PO)-SO₄ ⁻, or TDA-12(PO)-SO₄. The alcohol alkoxylated sulfate maybe a pure chemical or may be a mixture of different alcohol alkoxylatedsulfates.

In embodiment of the disclosure, the alcohol alkoxylated sulfatecomprises 0.1-15% by weight of the wellbore remediation composition tobe injected into a reservoir. In certain embodiments of the disclosurethe alcohol alkoxylated sulfate comprises 0.5% to 5% by weight of thewellbore remediation composition. In a specific embodiment, the alcoholalkoxylated sulfate comprises about 1% by weight of the wellboreremediation composition. In some embodiments, the alcohol alkoxylatedsulfate is used in a remediation composition in a low temperaturereservoir, such as reservoirs that are below 55° C. The specific alcoholalkoxylated sulfate used is generally tailored to the conditions of thereservoir needing damage remediation.

Alcohol Alkoxylated Carboxylate

Embodiments of the invention include the addition of an alcoholalkoxylated carboxylate in the remediation composition. The alcoholalkoxylated carboxylate has the general structure of alcohol-PO/EO-COO⁻,or a salt thereof. The alcohol group comprises 10-32 carbon atoms, andin specific embodiments comprises between 16 to 32, 13 to 17, or 10 to13 carbon atoms. In embodiments of the invention the PO/EO groupcomprises 0-50 ethylene oxide groups, 0-50 propylene oxide groups, orcombinations thereof. The alcohol alkoxylated carboxylate may be a purechemical or may be a mixture of different alcohol alkoxylatedcarboxylate

In embodiment of the disclosure, the alcohol alkoxylated carboxylatecomprises 0.1-15% by weight of the wellbore remediation composition tobe injected into a reservoir. In certain embodiments of the disclosurethe alcohol alkoxylated carboxylate comprises 0.5% to 5% by weight ofthe wellbore remediation composition. In a specific embodiment, thealcohol alkoxylated carboxylate comprises about 1% by weight of thewellbore remediation composition. The alcohol alkoxylated carboxylatemay be added to the composition when used high temperature reservoirs,such as reservoirs above 55° C. The specific alcohol alkoxylatedcarboxylate used is generally tailored to the conditions of thereservoir needing damage remediation.

Sulfosuccinate

As used herein, “sulfosuccinate” refers to a chemical having thestructure:

or a salt thereof, wherein R₁ is a branched or unbranched carbon chaincomprising 5 to 7 carbon atoms and wherein R₂ is a branched orunbranched carbon chain comprising 5 to 7 carbon atoms. In embodimentsof the disclosure, the sulfosuccinate is a sulfosuccinate salt, such asa sodium sulfosuccinate. In an embodiment, the sulfosuccinate is sodiumdihexyl sulfosuccinate, which are considered food grade, environmentallyfriendly compounds. In a specific embodiment, the dihexyl sulfosuccinatehas the following chemical structure:

In embodiment of the disclosure, the sulfosuccinate comprises 0.1-15% ofthe remediation composition to be injected into a wellbore. In certainembodiments of the disclosure the sulfosuccinate comprises 0.5% to 5% ofthe remediation composition. In a specific embodiment of the invention,the sulfosuccinate comprises about 1% of the remediation composition.The sulfosuccinate may be added to the remediation composition when usedin low temperature reservoirs, such as reservoirs below 55° C.Sulfosuccinates are commercially available chemicals, for example,sodium dihexyl sulfosuccinates are available from Cytec (MA-80-I, forexample). In an embodiment of the disclosure, the dihexyl sulfosuccinateis partially derived from a 4-methyl-2-pentanol feedstock. The specificsulfosuccinate used is generally tailored to the conditions of thereservoir needing damage remediation.

Additional Components

The remediation composition described throughout this disclosure mayinclude additional additives, such as alkali, chelators, co-solvents,polymers, and electrolytes. Chelators may be used to soften the water inthe solution or to reduce scaling in the formation. Examples ofchelators include ethylenediaminetetraacetic acid (EDTA) which can alsobe used as an alkali, methylglycinediacetic acid (MGDA). The amount ofchelant may be selected based on the amount of multivalent ions in thereservoir. For example, chelating agents can be used a 10:1 molar ratiowith divalent cations such as calcium or magnesium. Other chelatingagents may work depending on the brine composition and the desired pH.

Co-solvents may also be included in the slug compositions. Suitableco-solvents are alcohols, such as lower carbon chain alcohols likeisopropyl alcohol, ethanol, n-propyl alcohol, n-butyl alcohol, sec-butylalcohol, n-amyl alcohol, sec-amyl alcohol, n-hexyl alcohol, sec-hexylalcohol and the like; alcohol ethers, polyalkylene alcohol ethers,polyalkylene glycols, poly(oxyalkylene)glycols, poly(oxyalkylene)glycolsethers or any other common organic co-solvent or combinations of any twoor more co-solvents. For example, in an embodiment, an ether, ethyleneglycol butyl ether (EGBE), is used and typically is about 0.75 to 1.5times the concentration of total surfactant in the remediationcomposition. Generally, the co-solvent, such as EGBE, when used may bepresent in an amount of about 0.5 to about 6.0 by weight percent of thesolution to be injected into the reservoir, such as from about 0.5 toabout 4.0 by weight %, or about 0.5 to about 3 by weight %. In aspecific embodiment, the composition comprises 3.5% EGBE.

In one embodiment, alkali may be added to the remediation composition.The alkali employed is a basic salt of an alkali metal from Group IAmetals of the Periodic Table. In an embodiment, the alkali metal salt isa base, such as an alkali metal hydroxide, carbonate or bicarbonate,including, but not limited to, sodium carbonate, sodium bicarbonate,sodium hydroxide, potassium hydroxide, sodium silicate, tetrasodiumEDTA, sodium metaborate, sodium citrate, sodium tetraborate. The alkaliis typically used in amounts ranging from about 0.3 to about 5.0 weightpercent of the solution, such as about 0.5 to about 3 wt. %. Inembodiments, alkali is used in high temperature reservoirs, such asreservoirs above 55° C.

Water soluble polymers, such as those commonly employed for enhanced oilrecovery, can be included to control the mobility of the injectionsolution, such as through a polymer drive injected after the remediationcomposition or may be included within the composition. Such polymersinclude, but are not limited to, biopolymers such as xanthan gum andscleroglucan and synthetic polymers such as partially hydrolyzedpolyacrylamides (HPAMs or PHPAs) and hydrophobically-modifiedassociative polymers (APs). Also included are co-polymers ofpolyacrylamide (PAM) and one or both of 2-acrylamido 2-methylpropanesulfonic acid (and/or sodium salt) commonly referred to as AMPS (alsomore generally known as acrylamido tertiobutyl sulfonic acid or ATBS)and N-vinyl pyrrolidone (NVP). Molecular weights (Mw) of the polymersrange from about 100,000 Daltons to about 30,000,000 Daltons, such asabout 100,000 to about 500,000, or about 1,000,000 to about 20,000,000Daltons. In specific embodiments of the invention the polymer is about2,000,000 Daltons, about 8,000,000 Daltons, or about 20,000,000 Daltons.The polymer and the size of the polymer can be tailored to thepermeability, temperature and salinity of the reservoir.

EXAMPLES

The following examples are included to demonstrate specific embodimentsof the disclosure. It should be appreciated by those of skill in the artthat the techniques disclosed in the examples that follow representtechniques discovered by the inventors to function well in the practiceof the invention, and thus, can be considered to constitute modes forits practice. However, those skilled in the art should, in light of thepresent disclosure, appreciate that many changes can be made in thespecific embodiments disclosed and still obtain a like or similar resultwithout departing from the scope of the invention.

Example 1

It was necessary to ensure that polymer alone was not detrimental torelative permeability, so a baseline was obtained using powder polymerinstead of emulsion polymer. All core flood experiments describedthroughout were conducted according to known laboratory methods forreservoir cores. The core flood was set up using a reservoir sand pack,which was brine flooded, then oil flooded to initial oil saturation.After oil flooding, a secondary polymer flood was conducted using 2000ppm powder polymer for 1.3 PV. After polymer flood, the relativepermeability was calculated as 0.33 which suggested that polymer alonewas not contributing to a decrease in relative permeability. Next, itwas necessary to study the effects of the emulsion-dissolvingsurfactants in the absence of mineral oil so a composition comprising 1%sodium dihexyl sulfosuccinate, 1% TDA-4PO-SO₄, and 2000 ppm powderpolymer (no C₂₀-C₂₈ IOS) was injected into the core for about 2 PV (FIG.5, first arrow). The injection of only the sulfosuccinate and thealcohol alkoxylated sulfate resulted in essentially no change in krwwhich led to the conclusion that a third surfactant (responsible forsolubilizing the crude oil) should be added to the solution. A solutionof 1% by weight sodium dihexyl sulfosuccinate, 1% by weight TDA-8PO-SO4,1% by weight C₂₀-C₂₈ IOS, and 2000 ppm powder polymer was injected whichshowed an immediate increase in the relative permeability of the coreand an additional gradual increase (FIG. 5, second arrow) of over 2.5PV. The injection of the second composition resulted in an increase ofkrw by greater than a factor of 2.

Example 2

The core flood was set up using a reservoir sand pack, which was brineflooded, then oil flooded to initial oil saturation. After oil flooding,polymer flooding with 2000 ppm emulsion polymer (to simulate fieldconditions) began. After a krw of 0.18 was reached (at 11.2 PV), aremediation composition comprising 1% by weight sodium dihexylsulfosuccinate, 1% by weight TDA-8PO-SO₄, 1% by weight C₂₀-C₂₈ IOS, 3.5%by weight EGBE (used to reduce microemulsion viscosity), and 4000 ppmemulsion polymer (increased concentration for more favorable mobilityratio) was injected into the core. The relative permeability wascalculated (from recorded pressure) over the whole process and shown inFIG. 2. The remediation composition achieved a krw of 0.6 (at 14.5 PV)after starting at a damage relative permeability of 0.18 (at 11.2 PV).

Example 3

This core flood was performed to show the effectiveness of theremediation composition in the absence of high reservoir oil saturationand without emulsion polymer damage. The weathered oil from an activesand type reservoir was cleaned off for 5 PV using a remediationcomposition comprising 1% sodium dihexyl sulfosuccinate by weight, 1%TDA-8PO-SO₄ by weight, 1% C₂₀-C₂₈ IOS by weight, 3.5% by weight EGBE,and 4000 ppm emulsion polymer resulting in a krw of ˜0.95 (from 0-5 PV).After which the core was injected with emulsion polymer and damaged for15 more PVs until the krw=0.18 (5-20 PV). The same remediationcomposition was again injected into the core and achieved a krw of 0.73(20-24 PV). FIG. 3 illustrates the krw over PV injected for thedescribed series.

Example 4

The core flood was set up using a reservoir sand pack, which was brineflooded, then oil flooded to initial oil saturation. After oil flooding,the core was damaged for 27 PVs with emulsion polymer to a krw of 0.2.After which a remediation composition comprising 1% sodium dihexylsulfosuccinate, 1% TDA-BPO-SO₄ by weight, 1% C₂₀-C₂₈ IOS by weight, 3.5%EGBE by weight, and emulsion polymer was injected into the core andachieved a krw of 0.7. FIG. 4 illustrates the krw over PV injected forthe described series, with the injection of the surfactant compositionstarting at 27 PVs.

Example 5

The core flood was set up using a reservoir sand pack, which was brineflooded, then oil flooded to initial oil saturation. After oil flooding,10.5 PV of 2000 ppm emulsion polymer was injected to plug the core to akrw of 0.22 (FIG. 6, diamonds). After which 5 PV of a remediationcomposition with 1% by weight TDA-8(PO)-SO₄, 1% by weight sodium dihexylsulfosuccinate, and 1% by weight C₂₀-C₂₈ IOS was injected. After theremediation composition, another 2000 ppm polymer was injected. FIG. 6shows the change in krw as the different components were injected. Thesecond injection of polymer which occurred after the injection of theremediation composition shows about a 0.5 decrease in the change ofrelative permeability (about half the rate of damage). This core flooddemonstrates that the core is damaged at a slower rate after aremediation composition of the disclosure was used to clean it out.

Example 6

A “fish tank” core flood was set up using reservoir sand flooded with300 cP of reservoir oil. The core was water flooded for 3.5 PV(ROS=0.5), and then polymer flooded (45 cP) for 1 PV (ROS=0.25). Afterwhich snapshots were taken during a flood with a remediation compositioncontaining 1% by weight TDA-8(PO)-SO₄, 1% by weight sodium dihexylsulfosuccinate, 1% by weight C₂₀-C₂₈ IOS, and 3.5% EGBE. A 0.2 PV (100cP) slug of the remediation composition was injected, which was followedby a 1.3 PV polymer drive (100 cP) at an injection rate of 1 ft/day.FIGS. 7a-i are snapshots that were taken during the injection of theremediation composition and the polymer drive. The slugs were injectedinto the core at the injector 71 and removed at the producer 73.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the scope of theinvention as defined by the appended claims. Moreover, the scope of thepresent disclosure is not intended to be limited to the particularembodiments of the process, machine, manufacture, composition of matter,means, methods and steps described in the specification. As one ofordinary skill in the art will readily appreciate from the disclosure ofthe present invention, processes, machines, manufacture, compositions ofmatter, means, methods or steps, presently existing or later to bedeveloped that perform substantially the same function or achievesubstantially the same result as the corresponding embodiments describedherein may be utilized according to the present invention. Accordingly,the appended claims are intended to include within their scope suchprocesses, machines, manufacture, compositions of matter, means,methods, or steps.

REFERENCES

-   SPE 129766. Julian R. Barnes, Henk Dirkzwager, Jasper R. Smit,    Johan P. Smit, An On, Reinaldo C. Navarrete and Bob H. Ellison, and    Marten A. Buijse. “Application of internal olefin sulfonates and    other surfactants to EOR. Part 1: Structure—Performance    relationships for selection at different reservoir conditions.” SPE    Improved Oil Recovery Symposium, 24-28 Apr. 2010, Tulsa, Okla., USA-   U.S. Pat. No. 5,488,148-   U.S. Patent Application Publication 2009/0112014

What is claimed is:
 1. A method for remediation of existing damage in aregion near an injection wellbore in communication with a subterraneanreservoir wherein the injection wellbore is not intended for receivinghydrocarbons and wherein the existing damage is caused by previousinjection of a composition containing a polymer emulsion into theinjection wellbore, the method comprising injecting into thesubterranean reservoir a composition comprising an emulsion polymer, aC₂₀ internal olefin sulfonate, a C₁₅₋₁₈ internal olefin sulfonate, andan alcohol alkoxylated carboxylate, thereby dissolving, cleaning and/orflushing the polymer emulsion away from the injection wellbore.
 2. Themethod of claim 1, wherein the injection of the composition stimulatesthe region near the injection wellbore in communication with thesubterranean reservoir.
 3. The method of claim 1, wherein the injectionimproves the relative permeability of the region near the injectionwellbore in communication with the subterranean reservoir.
 4. The methodof claim 3, wherein the relative permeability of the region near theinjection wellbore in communication with the subterranean reservoir isincreased by at least 250 percent.
 5. The method of claim 1, wherein thetemperature of the region near the injection wellbore in communicationwith the subterranean reservoir is above 55° C.
 6. The method of claim5, wherein the composition further comprises an alkali.
 7. The method ofclaim 1, further comprising a co-solvent.